mt76: mt7921: fix a race between mt7921_mcu_drv_pmctrl and mt7921_mcu_fw_pmctrl

Introduce a mutex in order to avoid a race between mt7921_mcu_drv_pmctrl and
mt7921_mcu_fw_pmctrl routines since they are run two independent works

Fixes: 1d8efc74 ("mt76: mt7921: introduce Runtime PM support")
Signed-off-by: NLorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76_connac.h

@@ -54,6 +54,7 @@ struct mt76_connac_pm {
 
 	struct work_struct wake_work;
 	struct completion wake_cmpl;
+	struct mutex mutex;
 
 	struct delayed_work ps_work;
 	unsigned long last_activity;

drivers/net/wireless/mediatek/mt76/mt7921/init.c

@@ -222,6 +222,7 @@ int mt7921_register_device(struct mt7921_dev *dev)
 
 	INIT_DELAYED_WORK(&dev->pm.ps_work, mt7921_pm_power_save_work);
 	INIT_WORK(&dev->pm.wake_work, mt7921_pm_wake_work);
+	mutex_init(&dev->pm.mutex);
 	init_completion(&dev->pm.wake_cmpl);
 	spin_lock_init(&dev->pm.txq_lock);
 	set_bit(MT76_STATE_PM, &dev->mphy.state);

drivers/net/wireless/mediatek/mt76/mt7921/mcu.c

@@ -1267,9 +1267,11 @@ int mt7921_mcu_set_bss_pm(struct mt7921_dev *dev, struct ieee80211_vif *vif,
 int mt7921_mcu_drv_pmctrl(struct mt7921_dev *dev)
 {
 	struct mt76_phy *mphy = &dev->mt76.phy;
-	int i;
+	int i, err = 0;
 
-	if (!test_and_clear_bit(MT76_STATE_PM, &mphy->state))
+	mutex_lock(&dev->pm.mutex);
+
+	if (!test_bit(MT76_STATE_PM, &mphy->state))
 		goto out;
 
 	for (i = 0; i < MT7921_DRV_OWN_RETRY_COUNT; i++) {
@@ -1281,23 +1283,30 @@ int mt7921_mcu_drv_pmctrl(struct mt7921_dev *dev)
 
 	if (i == MT7921_DRV_OWN_RETRY_COUNT) {
 		dev_err(dev->mt76.dev, "driver own failed\n");
-		mt7921_reset(&dev->mt76);
-		return -EIO;
+		err = -EIO;
+		goto out;
 	}
+	clear_bit(MT76_STATE_PM, &mphy->state);
 
 out:
 	dev->pm.last_activity = jiffies;
+	mutex_unlock(&dev->pm.mutex);
 
-	return 0;
+	if (err)
+		mt7921_reset(&dev->mt76);
+
+	return err;
 }
 
 int mt7921_mcu_fw_pmctrl(struct mt7921_dev *dev)
 {
 	struct mt76_phy *mphy = &dev->mt76.phy;
-	int i;
+	int i, err = 0;
+
+	mutex_lock(&dev->pm.mutex);
 
 	if (test_and_set_bit(MT76_STATE_PM, &mphy->state))
-		return 0;
+		goto out;
 
 	for (i = 0; i < MT7921_DRV_OWN_RETRY_COUNT; i++) {
 		mt76_wr(dev, MT_CONN_ON_LPCTL, PCIE_LPCR_HOST_SET_OWN);
@@ -1308,11 +1317,16 @@ int mt7921_mcu_fw_pmctrl(struct mt7921_dev *dev)
 
 	if (i == MT7921_DRV_OWN_RETRY_COUNT) {
 		dev_err(dev->mt76.dev, "firmware own failed\n");
-		mt7921_reset(&dev->mt76);
-		return -EIO;
+		clear_bit(MT76_STATE_PM, &mphy->state);
+		err = -EIO;
 	}
+out:
+	mutex_unlock(&dev->pm.mutex);
 
-	return 0;
+	if (err)
+		mt7921_reset(&dev->mt76);
+
+	return err;
 }
 
 void